.\"	$OpenBSD: SSL_connect.3,v 1.6 2018/03/27 17:35:50 schwarze Exp $
.\"	OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100
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.Dd $Mdocdate: March 27 2018 $
.Dt SSL_CONNECT 3
.Os
.Sh NAME
.Nm SSL_connect
.Nd initiate the TLS/SSL handshake with a TLS/SSL server
.Sh SYNOPSIS
.In openssl/ssl.h
.Ft int
.Fn SSL_connect "SSL *ssl"
.Sh DESCRIPTION
.Fn SSL_connect
initiates the TLS/SSL handshake with a server.
The communication channel must already have been set and assigned to the
.Fa ssl
by setting an underlying
.Vt BIO .
.Pp
The behaviour of
.Fn SSL_connect
depends on the underlying
.Vt BIO .
.Pp
If the underlying
.Vt BIO
is
.Em blocking ,
.Fn SSL_connect
will only return once the handshake has been finished or an error occurred.
.Pp
If the underlying
.Vt BIO
is
.Em non-blocking ,
.Fn SSL_connect
will also return when the underlying
.Vt BIO
could not satisfy the needs of
.Fn SSL_connect
to continue the handshake, indicating the problem with the return value \(mi1.
In this case a call to
.Xr SSL_get_error 3
with the return value of
.Fn SSL_connect
will yield
.Dv SSL_ERROR_WANT_READ
or
.Dv SSL_ERROR_WANT_WRITE .
The calling process then must repeat the call after taking appropriate action
to satisfy the needs of
.Fn SSL_connect .
The action depends on the underlying
.Vt BIO .
When using a non-blocking socket, nothing is to be done, but
.Xr select 2
can be used to check for the required condition.
When using a buffering
.Vt BIO ,
like a
.Vt BIO
pair, data must be written into or retrieved out of the
.Vt BIO
before being able to continue.
.Sh RETURN VALUES
The following return values can occur:
.Bl -tag -width Ds
.It 0
The TLS/SSL handshake was not successful but was shut down controlled and
by the specifications of the TLS/SSL protocol.
Call
.Xr SSL_get_error 3
with the return value
.Fa ret
to find out the reason.
.It 1
The TLS/SSL handshake was successfully completed,
and a TLS/SSL connection has been established.
.It <0
The TLS/SSL handshake was not successful, because either a fatal error occurred
at the protocol level or a connection failure occurred.
The shutdown was not clean.
It can also occur if action is needed to continue the operation for
non-blocking
.Vt BIO Ns s .
Call
.Xr SSL_get_error 3
with the return value
.Fa ret
to find out the reason.
.El
.Sh SEE ALSO
.Xr BIO_new 3 ,
.Xr ssl 3 ,
.Xr SSL_accept 3 ,
.Xr SSL_CTX_new 3 ,
.Xr SSL_do_handshake 3 ,
.Xr SSL_get_error 3 ,
.Xr SSL_set_connect_state 3 ,
.Xr SSL_shutdown 3
.Sh HISTORY
.Fn SSL_connect
appeared in SSLeay 0.4 or earlier and has been available since
.Ox 2.4 .
